physics p1

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Cards (121)

what are the 4 ways energy is transferred
Mechanically
electrically
by heating
by radiation
What is a system?
a single object or a group of objects
what happens when a system changes
energy is transfered
what is the net change in the total energy of a closed system
always zero
What is work done? 
energy transferred
When can work be done? 
When a current flows
By a force moving an object
what is movement energy
kinetic energy
What does kinetic energy depend on?
mass and speed
more mass the faster
what does raised objects store energy in
gravitational potential
What does GPE depend on?
mass and height
what energy transfer occurs when something falls
GPE TRANSFERS TO KE
what does stretching transfer energy to
Elastic potential energy
What is specific heat capacity? 
How hard it is to heat something up
What is the conservation of energy principle
energy can be transferred usefully but can never be created or destroyed
What is dissipated energy?
wasted energy
What is power?
the rate of doing work
e.g how much per second
What is power measured in?
Watts
How can you reduce frictional forces? 
lubrication
How can heating occur?
conduction and convection
what happens when a object is heated
what is conduction
energy transfer to kinetic
particles vibrate and collide (conduction)
what happens in convection
when a object is heated
convection is a heat transfer process
cooler particles at bottom
warmer particles at top
what does insulation reduce the rate of
energy transfer by heating
what are cavity walls in houses
cavity wall air gap is filled with a foam and can reduce energy transfer by convection
Where does convection occur? 
liquids and gases
where does conduction occur 
solids
what does radiation use
infrared
What is convection?
The transfer of heat by the movement of a fluid
hot particles rise to the top release heat and then condense and go down where cooler particles get hot then repeats cycle
what takes place in conduction
energy spreads
What can loft insulation reduce
convection currents
what do double glazed windows do
Prevent energy transfer by conduction through the windows
What do draught excluders do?
Reduce energy transfers by convection
the less energy which is wasted...
the more efficient the device is
what is the only device with is 100% efficient
electric heaters
all energy is transferred to useful thermal energy stores
what are examples of non renewable sources
coal
oil
gas
fossil fuels
What are renewable sources of energy?
solar
wind
water waves
biofuel
tides
geothermal
what can energy sources be used for
transport
tranportation energy sources
coal , petrol and diesel
biofuels
heating energy sources
natural gas
coal
electric heaters
geothermal
solar water heaters
biofuel
What is an advantage of wind energy
no pollution or greenhouse gases produced
what is a disadvantage of wind energy
can produce noise pollution